1. Field of the Invention
The invention relates to a method and a device for displaying ordinate-abscissa value pairs on a display device.
2. Discussion of the Background
Display devices with discrete display points—pixel graphics—are currently used as standard for the graphic display of measured values in measuring instruments or systems, for example, spectrum analysers and network analysers. The resolution of such display devices is limited because of the limited number of display points in ordinate and abscissa direction. The maximum resolution of display devices of this kind is currently, for example, around 1000·600 display points.
With a spectrum analyser according to the prior art, as shown in FIG. 1, with a low-pass filter 1 for frequency limitation of the signal to be displayed with regard to the sampling theorem, an analog-digital converter 2 for digitization of the signal to be displayed, a fast Fourier transformer 3 (FFT) for calculating the discrete Fourier spectral lines by fast Fourier transform, a modulus former 4 for determining the power-spectral lines, a log unit 5 for compression of the power-spectral lines scattering over a wide signal range to the display range of the display device and a display device 6 with discrete display points in ordinate and abscissa direction for displaying the discrete power-spectral lines, the power spectrum to be displayed provides in the abscissa direction a resolution at the level of the FFT length NFFT of the FFT transformer 3—typically NFFT=2048—and in the ordinate direction a resolution at the level of the word width of the log unit 5—typically 216=56636 level stages. Since the resolution of the measured values to be displayed is greater both in abscissa and also in ordinate direction than the resolution of the display device 6, the resolution of the measured values to be displayed must be reduced before implementing the display of the measured values on the display device 6.
Regarding the prior art, reference is made to U.S. Pat. No. 5,103,402.
A reduction in the resolution of the measured values to be displayed in the abscissa direction leads disadvantageously to a loss of information in the measured values to be displayed in the ordinate direction. Strong fluctuations in the measured values to be displayed over a relatively wide value range in the ordinate direction accordingly bring about an unacceptable loss of accuracy, in particular in the case of a real-time data acquisition and display.